Is it odd for a 2 yr old to have a cough for almost 4 months ? My little niece has had it for so…

Is it odd for a 2 yr old to have a cough for almost 4 months ? My little niece has had it for so long, my sister says it’s nothing wrong but idk 😐

And she don’t really speak at all, I mean I don’t know if that’s a red flag or it’s normal I’m not her mother so I can’t say much but i was just wondering if any of you moms had a Similar situation.